The fact that the passengers did not hear or pay attention to the safety briefing given on the wharf suggests that it was not delivered under appropriate conditions. The MED course required for higher certificates initiates mariners to safety measures to be taken in an emergency. Assembling the passengers to brief them on emergency measures in not required by existing regulations except on passenger vessels making voyages of more than 24hours. The crew did not warn the four passengers of the risk involved in standing on the seat. As the stern railing was bolted to the slanted back of the seat, the railing was aft of the hinges on the hatch cover. The passengers standing on the seat and leaning on the seat back and railing produced a lever effect, because their weight exerted a force behind the hinges. As the engine compartment hatch cover was not fitted with a safety catch to secure it shut, the hatch cover tipped back when a passenger standing near the step went down onto the lower deck. The railing was fastened to the seat back by bolts passing through the stays and the back. The weight of the four passengers caused the railing stays in way of the top bolts to give way. The boat held a valid inspection certificate, but the railing was being used for purposes other than those for which it was designed. The anchoring points at the top of the hydraulic cylinders gave way when the platform tipped back.Analysis The fact that the passengers did not hear or pay attention to the safety briefing given on the wharf suggests that it was not delivered under appropriate conditions. The MED course required for higher certificates initiates mariners to safety measures to be taken in an emergency. Assembling the passengers to brief them on emergency measures in not required by existing regulations except on passenger vessels making voyages of more than 24hours. The crew did not warn the four passengers of the risk involved in standing on the seat. As the stern railing was bolted to the slanted back of the seat, the railing was aft of the hinges on the hatch cover. The passengers standing on the seat and leaning on the seat back and railing produced a lever effect, because their weight exerted a force behind the hinges. As the engine compartment hatch cover was not fitted with a safety catch to secure it shut, the hatch cover tipped back when a passenger standing near the step went down onto the lower deck. The railing was fastened to the seat back by bolts passing through the stays and the back. The weight of the four passengers caused the railing stays in way of the top bolts to give way. The boat held a valid inspection certificate, but the railing was being used for purposes other than those for which it was designed. The anchoring points at the top of the hydraulic cylinders gave way when the platform tipped back. The passengers were not formally assembled at the start of the cruise. The crew did not provide an effective safety briefing to inform the passengers of measures to be taken in case of emergency. Four passengers stood up on the stern seat. The crew did not ask the four passengers to sit back down on the seat. The engine compartment hatch cover which served as the observation deck at the stern was not fitted with safety catches to prevent it from tipping back. The weight of the passengers leaning on the seat back and railing produced a lever effect that caused the hatch cover to tip back. The stern railing gave way under the weight of the four passengers. The passengers were not wearing lifejackets nor were they required to do so by regulations. The tour boat retrieved the passengers from the water safe and sound.Findings The passengers were not formally assembled at the start of the cruise. The crew did not provide an effective safety briefing to inform the passengers of measures to be taken in case of emergency. Four passengers stood up on the stern seat. The crew did not ask the four passengers to sit back down on the seat. The engine compartment hatch cover which served as the observation deck at the stern was not fitted with safety catches to prevent it from tipping back. The weight of the passengers leaning on the seat back and railing produced a lever effect that caused the hatch cover to tip back. The stern railing gave way under the weight of the four passengers. The passengers were not wearing lifejackets nor were they required to do so by regulations. The tour boat retrieved the passengers from the water safe and sound. Four passengers fell overboard off the CANARD MALARD because they stood up on the stern seat and the crew did not require them to get back down on the deck. The engine compartment hatch cover, which served as the stern observation deck, tipped back because it was not fitted with a fastening device. The stern railing gave way under the weight of the four passengers.Causes and Contributing Factors Four passengers fell overboard off the CANARD MALARD because they stood up on the stern seat and the crew did not require them to get back down on the deck. The engine compartment hatch cover, which served as the stern observation deck, tipped back because it was not fitted with a fastening device. The stern railing gave way under the weight of the four passengers. Since the occurrence, two safety catches have been installed on the front of the platform, and a new stern railing has been secured to the side railings and the deck. In addition, the anchoring plate has been bolted down with locknuts. These alterations were carried out under the supervision of a Transport Canada Marine Safety inspector.Safety Action Taken Since the occurrence, two safety catches have been installed on the front of the platform, and a new stern railing has been secured to the side railings and the deck. In addition, the anchoring plate has been bolted down with locknuts. These alterations were carried out under the supervision of a Transport Canada Marine Safety inspector.